Amazon.com: 250GB - Samsung 840 Series Solid State Drive (SSD) with Desktop and Notebook Installation Kit 250 sata_6_0_gb 2.5-Inch MZ-7TD250KW: Computers & Accessories.
If you want to speed up your notebook by a factor of 5, the best add on you can buy is an SSD drive. Solid State drives don't make noise, have no moving parts, and make a notebook computer boot in under 30 seconds. You can get the bare drive for around $20 less; but, unless you know you don't need the mounting hardware, and unless you are willing to search Samsung for the data transfer apps, spend the extra money and get the complete kit. In addition to the speed increase, it is very calming to know that I don't have to worry about a mechanical drive being destroyed if I drop the computer. Nothing is indestructible; but these modern SSD drives are pretty stable, and now have enough storage, and are cheap enough, that I wouldn't have a computer without one. If you need more than 250 Gigs of storage, you can get a 500 Gig version now for around $400.